The purpose of the present invention is to increase the combustion efficiency of a gun type burner employing a liquid fuel atomizing nozzle discharging a conical fuel spray. Exemplary of a conventional fuel nozzle which may be employed with a standard 4" diameter air blast tube as original equipment or retrofit of a conventional gun type burner is a 0.75 g.p.h. nozzle discharging an 80.degree. spray pattern. The improved gun burner may be employed with a wide variety of conventional heating systems such as, for example, a Lux-air hot air furnace, model OU1OOMF manufactured by Lux-Air Corporation of Elyria, Ohio.
Conventional gun burners, although employing atomizing fuel injectors having conical spray patterns, usually introduce primary air in such fashion that mixing takes place and upstream combustion initiates within a generally cylindrical zone centrally of the blast tube. This by virtue of the manner in which primary air is introduced. Thus, whether most of the required primary air be introduced along a swirling path concentric with the fuel injector to intersect the conical fuel spray and entrain the same or the primary air stream be split to include mixing components both projecting the fuel spray downstream and introducing air radially inwardly through a perforated, generally cylindrical portion of a burner can, the result is the same; "choking" or constriction of the mixing zone and flame pattern. Even with such a choking effect it is still possible to achieve substantially complete mixing albeit over a somewhat longer distance and requiring a greater excess of air over a theoretical stoichiometric mix than would be required if the mixing zone were less constricted. Although, from the latter, it might appear immaterial whether a stoichiometric mix takes place over a greater or lesser axial distance and/or requiring a greater or lesser excess of primary air; such is not the case. Significent improvements result when, other factors being equal, the primary air requirement can be reduced. Thus where less air is required to achieve the same mixing; the extra energy requirements to heat and move the extra air are eliminated and, with less air flow requirement, air velocity is accordingly reduced thus increasing residence time of the combustion process, increasing heat exchange time with the heating medium and reducing stack temperatures.
While some of the theoretical considerations underlying the dramatic increase in combustion efficiency of the burner assembly herein disclosed as compared with various conventional assemblies are not fully understood, the empirical results of independent comparative testing are fully documented.